SIDDS, or Simulations in Developmental Disabilities, is a computer system designed to provide undergraduate students with the opportunity to acquire and practice skills in behavioral psychology. During the computer simulation, the student assumes the role of a behavior analyst whose professional duties involve the assessment and treatment of the severe problem behavior displayed by a child with a developmental handicap. The specific instructional objectives of SIDDS include teaching undergraduate psychology students to: (a) operationally define the target behavior: (b) select the relevant behavioral assessments for the client case; (c) interpret graphed data of the client's behavior; (d) formulate a functional hypothesis concerning the cause of the client's behavior problem; (e) choose an effective treatment plan; and (f) evaluate the effectiveness of treatment by analyzing graphical representations of the client's behavior. Although a prototype version of SIDDS has been created, further refinement of it is necessary to ensure the development of a quality system. The objective of this grant is to expand the number of client cases included in SIDDS, enhance the instructional features of the courseware (e.g., by adding a tutorial, point system of student feedback: and video display of the client's behavior), and evaluate its effectiveness in teaching behavioral assessment and treatment decision-making skills to students. Evaluative studies will include: (a) determining whether the content of SIDDS is accurate and valid; (b) assessing whether SIDDS teaches clinically relevant skills; (c) assessing student perception of SIDDS; (d) comparing students' test results prior to and following use of SIDDS: (e) determining whether students generalize the skills taught to new client cases: (f) comparing student performance on tests delivered prior to and following computer presentation versus instructor presentation versus combined computer-instructor presentation of the content material: and (g) performing a cost-effectiveness analysis of computer versus instructor presentation of the content material. In addition to the development of a computer program, it is expected that a method of testing courseware will result from this project, which will be useful in the development of other instructional products.